The present invention relates to an industrial waste crushing bit used for finely crushing industrial wastes or the like.
Conventionally, an industrial waste crusher (also referred to as xe2x80x9ctub grinderxe2x80x9d) used for crushing, for example, lumbers, etc. is comprised of a tub having an opening at the top to which industrial wastes are supplied, a rotary hammer placed on the bottom of the tub and a number of bits attached to the rotary hammer and is designed such that the industrial wastes fed into the tub are crushed by rotating the rotary hammer and discharged outside the machine. Here, with respect to the bit, as disclosed in U.S. Pat. No. 5,611,496 or in International Publication No. 95/18678, a bit, which has a structure in which a super-hard member is inserted in the tip of a bit body and brazed therein is generally used.
As illustrated in FIG. 12, in a bit 50 having the conventional structure, the bit body is constructed such that a head 52 having a virtually cone shape is provided at the leading end of a shank 51 through a flange 54, and a super-hard member 53 is inserted into and secured to a recessed section formed in the tip of the head 52 by brazing, etc. Moreover, the rear part of the shank 51 is died to form a thread which, in turn, is secured to a hammer body (not shown) by means of a nut. Here, with respect to the super-hard member 53, as illustrated in FIGS. 12(b) and 12(c) showing cross sections taken along lines Exe2x80x94E and Fxe2x80x94F of FIG. 12(a), respectively, a member which has a circular shape in its cross section and a virtually column shape with its top machined into a round shape like a bullet is adopted.
Moreover, in the member having such a shape, in order to improve the service life of the bit tip against wear, build up welding is often applied to the entire bit tip or only to portions susceptible to wear by using a high-hardness material or a material mixed with high-hardness particles.
However, the problem with this type of bit is that an initial wear G1 (FIG. 13(a)) which is created in the tip on the front side of the head 52 in the rotational direction and initial wear G2 (FIG. 13(b)) which is created on the right and left sides of the head 52 in the rotational direction develop rapidly, causing a reduction in the brazed area for the super-hard member 53 and a lack of holding strength. As a result, the service life of the bit is shortened.
In order to cope with the above-mentioned problem, one proposal is to increase the length of the super-hard member so as to improve the service life against wear. However, increase in the length of the super-hard member results in high cost, as well as increase in the length of an exposed head of the super-hard member 53 due to the progress of the initial wear G1 and G2, thereby causing another problem in which the super-hard member 53 will be easy to break and to fall out of the bit body. Since the bit is used in a high-speed rotating state, if the super-hard member is broken or falls out during operation (while the bit is in rotation), the broken super-hard member might jump out of the industrial waste crusher, which is extremely dangerous.
Moreover, even when overlaying is applied to the entire bit tip or only to portions susceptible to wear by using a high-hardness material, since it cannot obtain wear resistance as high as the super-hard member, the tip on the front side, and the right and left sides of the head 52 in the rotational direction wear quickly at an early stage. Such wear on the head 52 leads to a significant decrease in the crushing efficiency.
Moreover, another problem is that since the recessed section into which the super-hard member 53 is inserted from the tip of the head 52 and brazed is available only on the tip side, gas generated at the time of brazing is hardly released, as a result of which a defective brazed tip tends to be formed.
The present invention is directed to overcoming the foregoing problems, and the primary object of the invention is therefore to provide an industrial waste crushing bit which is capable of sufficiently exerting wear resistance from the initial stage of service and has a longer service life at low cost.
The above object can be accomplished by an industrial waste crushing bit according to a first aspect of the invention, the industrial waste crushing bit comprising a bit body having an opening formed at the tip thereof, and a super-hard member inserted therein,
wherein the super-hard member is formed into a virtually plate shape and the plate faces of the super-hard member are placed in a direction virtually orthogonal to the rotational direction of the bit, with the side faces of the super-hard member being exposed.
In accordance with the invention, the super-hard member having a virtually plate shape is embedded in the bit body with its side faces being exposed, and the plate faces of the super-hard member are placed in a direction virtually orthogonal to the rotational direction of the bit. Therefore, each exposed side face functions effectively in crushing materials to be crushed. In other words, this can solve the problem of progress of the initial wear G2, which sufficiently contributes to exertion of wear resistance from the initial stage of service and extends the bit service life as a whole. Moreover, since an expensive super-hard material is used only for portions susceptible to wear, the amount of the super-hard material to be used can be saved, thereby realizing lowering of cost. It should be noted here that the xe2x80x9cvirtually plate shapexe2x80x9d refers to a shape which has a width in the rotational direction that is shorter than a length in a direction orthogonal to the bit rotational direction and is a plate-like shape as a whole.
Preferably, the thickness of the virtually plate-shaped super-hard member is set in the range of 0.1 to 0.5 times the outer diameter of the head of the bit body. If the value is less than 0.1 times the outer diameter of the head, the thickness of the super-hard member becomes so thin that upon contact with materials to be crushed, the super-hard member is more likely to be damaged, failing to provide a sufficient wear-resistant effect. On the other hand, if the value exceeds 0.5 times the outer diameter of the head, the bit body portion supporting the super-hard member becomes relatively small, as a result of which when the bit body portion wears, the super-hard member is more likely to fall out, the bit head is more likely to be damaged, and the cost of the super-hard member becomes higher, resulting in inevitably higher cost as a whole bit.
With respect to the shape of each wall face of the opening, it is preferable to form each wall face into a tapered shape expanding inward while the super-hard member is so formed as to fit the shape of the wall face. Moreover, it is also preferable to form it into a shape having a recess inward at least on one side in the width direction of the super-hard member, while the super-hard member is so formed as to fit the shape of the wall face. With this arrangement, even when the bit is used in a high-speed rotating state, the super-hard member can be prevented, without fail, from falling out due to the centrifugal force accompanied with the rotation.
Furthermore, it is preferable that a theft be formed in the tip on the front side of the bit body in the rotational direction and that build up welding be applied to the theft by using a high-hardness material or a material mixed with high-hardness particles. With this arrangement, the initial wear occurring in the tip on the front side, and on the right and left sides of the bit body in the rotational direction can be suppressed without increasing the amount of expensive super-hard member, thereby improving the bit service life.
In the invention, the bit body is preferably comprised of a head at the front through a flange, and it is preferable to apply build up welding to at least the front side of these head and flange in the rotational direction by using a high-hardness material or a material mixed with high-hardness particles. This arrangement improves wear resistance at least on the front side of the head and the flange in the rotational direction, the place with which materials to be crushed come into contact, thereby preventing the attached bit body from becoming unstable due to wear on the flange and the crushing efficiency from decreasing, and further lengthening the service life.
Moreover, it is preferable to put a mark in the lower part at least on either one of the side faces of the super-hard member in the width direction, indicating a limit position beyond which the danger of falling-out of the super-hard member due to wear of the bit body is expected. Although the super-hard member will finally fall out of the bit body thereby to finish its service life and its limit of wear when it falls out varies depending upon the size and shape of the head and the super-hard member, it can be judged through experience to what extent of exposure of the super-hard member due to wear on the front side of the bit body in the rotational direction causes the super-hard member to fall out. Therefore, by putting the mark in the lower part at least on either one of the side faces of the super-hard member in the width direction, indicating a limit position beyond which the danger of falling-out of the super-hard member is expected due to wear of the bit body, that is the position in height determined based upon the above-mentioned experience, even an unskilled worker can easily make a judgment as to the expiration of the service life and avoid the danger of falling-out of the super-hard member during operation (while the bit is in rotation).
Moreover, in the invention, the bit body and the super-hard member are preferably joined to each other by means of brazing.
According to a second aspect of the invention, there is provided an industrial waste crushing bit, the industrial waste crushing bit comprising a bit body having an opening formed at the tip thereof, and a super-hard member inserted therein,
wherein the super-hard member is formed into a virtually plate shape and the plate faces of the super-hard member are placed in a direction virtually orthogonal to the rotational direction of the bit, with the front face of the super-hard member in the rotational direction being formed into a slanting shape having the width in the vicinity of the tip set wider than the width of the base, while the front face in the tip of the super-hard member being exposed.
In the invention, the width in the vicinity of the tip of the super-hard member is set wider than the width of its base, and the front face in the tip of the super-hard member in the rotational direction is exposed from the bit body so that the front face of the super-hard member in the rotational direction works effectively in crushing materials to be crushed while suppressing the initial wear occurring in the tip on the front side of the bit body in the rotational direction, as a result of which the crushing operation is efficiently carried out. Therefore, the invention enables suppression of initial wear occurring in the tip on the front side of the bit body in the rotational direction, sufficient contribution to exertion of wear resistance at the initial stage of service and extending of the service life as a whole. Moreover, since the expensive super-hard member is used only for portions susceptible to wear, lowering of cost can be attained, and the efficiency of crushing materials to be crushed can be improved. It should be noted that the super-hard member is secured to the bit body in a manner so as to expose its side faces, which can simultaneously suppress the initial wear occurring in the tip on the front side of the bit body in the rotational direction and the initial wear occurring on the right and left sides thereof in the rotational direction and consequently, increase the service life.
In the invention, the exposed part on the tip front face of the super-hard member in the rotational direction is preferably made flush with the front face of the bit body.
In the invention, the bit body is preferably comprised of a head at the front through a flange, and it is preferable to apply build up welding to at least the front side of these head and flange in the rotational direction by using a high-hardness material or a material mixed with high-hardness particles. Moreover, it is preferable to put a mark in the lower part at least on either one of the side faces of the super-hard member in the width direction, indicating a limit position beyond which the danger of falling-out of the super-hard member due to wear of the bit body is expected. Furthermore, the bit body and the super-hard member are preferably joined to each other by means of brazing. With respect to the super-hard member, it is preferable to use a super-hard material that is formed by combining one or more high-hardness elements selected from the group consisting of carbide, nitride, boride and diamond with a metal.